Yll and Ylla
They are a couple in "Ylla" and represent the strained relationships of many American couples in the 1950's and 1960's. Yll is extremely jealous of Ylla's dreams that she has of meeting Earthmen. Yll's jealousy forces him to trick Ylla into staying home so that he can kill the Earthmen.
Nathanial York
He is the captain of the first expedition. He, along with his partner, Bert, get killed by Yll due to Yll's jealousy.
Captain Williams
He is the captain of the second expedition. When he lands on Mars, he and his men go around knocking on people's doors hoping to cause some excitement. The Martians are annoyed at his behavior, so one of the Martians tricks him into signing a paper that allows them to be put into an insane asylum and euthanized.
John Black
He is the captain of the third expedition. He is a rational person who thinks of the dangers before he goes out into the Earthian town. Even though he does not want his crew to interact with their dead family members, he eventually reluctantly allows them to. He meets his dead relatives and he goes to sleep with them. In the middle of the night, he awakes and correctly recognizes that he has fallen into a trap and unsuccessfully tries to escape before his dead family members kill him.
Captain Wilder
He is the captain of the fourth expedition. He believes that the crew can celebrate the accomplishment of getting to Mars but also believes that the crew should have some respect for the ancient Martian civilizations. However, he disagrees with Spender's violent methods to prevent people from colonizing Mars. He tries to reason with Spender but is unsuccessful so he is forced to reluctantly shoot him. After the colonization of Mars begins, he is sent to explore Jupiter and Pluto so that he would not interfere with the colonization. He returns to Mars in 2026 on his way back to Earth and meets up with Hathaway, who he tries to help but is unsuccessful at saving him.
Biggs
Biggs is an ignorant, disrespectful member on the fourth expedition who wants to party and destroy Martian civilization. He is okay with vandalizing the ancient Martian cities and vomits in the middle of one of them. His irresponsible actions lead to Spender shooting and killing him.
Spender
Spender is one of the men on the fourth expedition and the only one who fully respects the Martian civilization. He is adverse to the idea of colonizing Mars and is willing to use violence to prevent colonization. He is disgusted by the actions that Biggs does and he pushes him into a river when he parties too hard. When he sees Biggs vomit in the middle of one of the Martian cities, he gets angry and ditches the group. He comes back a few days later and kills Biggs and tries to get the rest of the crew on his side. When the crew refuses, he kills all of the ones that he talked to. He then retreats into the mountain and Captain Wilder and a few other men try to pursue him. Captain Wilder tries to stop him and Spender explains to him why he has to defend Mars from colonization. Later when he is attacked, he holds his ground and Captain Wilder is reluctantly forced to shoot him.
Sam Parkhill
Sam is an ignorant, disrespectful member on the fourth expedition, like Biggs. His actions are similar to the ones of Biggs and he shows a disrespect for the Martian civilization. He survives Spender's attacks and goes with Captain Wilder to kill Spender. He has a deep hatred of Spender for killing over half of the crew and does not understand his reasoning. After Captain Wilder kills Spender, Parkhill goes off and shoots the windows of the Martian city for target practice. As a result, Captain Wilder knocks his teeth out. Later after Mars has been colonized, Parkhill hopes to open the best hot dog stand on the planet. He chooses to open his hot dog stand at the intersection of two ancient Martian highways, hoping that once the Earthmen arrive in Mars in large numbers, he will have a good business. But one day a few Martians appear asking him for something. Parkhill panics and kills them. Later a group of Martians come and Parkhill tries to outrun the Martians on a sand barge. The Martians catch up to him and give him something surprising: half of Mars. Parkhill is ecstatic but the nuclear war on Earth starts that very night, ruining his plans.
